ABSTRACT The Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) is a longitudinal birth cohort of ~600 primarily first-generation Mexican American children living in the agricultural Salinas Valley, California. CHAMACOS was formed with the same intent as ECHO: to examine the association of early life environmental exposures with birth outcomes, neurodevelopment, respiratory health, and obesity. We have followed children from in utero through adolescence and we now propose to follow them into adulthood. Over the past 17 years, we have developed effective strategies to enroll, track, and retain study participants in this low-income Latino population; we have succeeded in collecting high quality data on all four endpoints of focus for ECHO; we have collected, processed, shipped, and stored over 150,000 varied biological and environmental samples; we have measured over 100 chemical exposures; we have helped develop and test sophisticated and novel exposure, genetic, and epigenetic laboratory assays; and we have developed a solid community-university partnership, earning the trust of participants and community stakeholders. Thus, CHAMACOS could serve as a model birth cohort for ECHO, rare in its length and breadth of assessment of children from birth to adulthood, offering valuable methodologies, lessons learned, and opportunities to the larger ECHO consortium. In addition, CHAMACOS contributes to ECHO a select, high-risk population of Latino children in a farmworker community . As 60% of this cohort is overweight or obese, we also offer data on children at high risk of metabolic, cardiovascular, and liver disease. Because the CHAMACOS children are approaching adulthood, we are uniquely positioned to examine the early origins of adult disease and address important gaps in the relationship between early life exposures and multiple health endpoints. We have reported that in utero organophosphate pesticide (OP) exposure is associated with poorer attention and executive function, lower IQ, respiratory symptoms, and poorer lung function at school-age. In the UG3 phase, we aim to test new methods that will expand our understanding of these relationships and contribute cutting-edge methodologies to ECHO. We propose to: 1) examine a newly-studied epigenetic modification, hydroxyl-methylcytosine (5-hmC) ? a potentially strong candidate for understanding the molecular mechanisms underlying effects on neurodevelopment; and 2) apply near infrared spectroscopy (fNIRs) for functional neuroimaging ? an inexpensive and convenient alternative to functional MRI. In the UH3 phase, we propose to follow-up participants at age 18 and 21 to assess the effects of in utero and early childhood exposure to agricultural pesticides on: 1) neurobehavioral endpoints; 2) respiratory symptoms and function; and 3) body mass and related metabolic and cardiovascular conditions. This valuable cohort has the potential to add rich data, validated protocols, and practical experience to the ECHO consortium, while also answering vital questions about the long-term sequelae of prenatal and early life exposure to pesticides on adult health.